Ntn discontinuous coverage and periodically attempt to obtain service on higher priority plmn

Abstract

A method of periodically attempting to access the HPLMN or an EHPLMN with higher priority in NTN systems with discontinuous coverage is proposed. A UE registered in VPLMN starts a timer T to periodically attempt to obtain service on its HPLMN or EHPLMN. When access stratum is deactivated due to discontinuous coverage in NTN, the UE does not stop the timer T, and postpone the periodic attempts to a later time, e.g., upon or after the UE activates the access stratum.

What is claimed is: 
     
         1 . A method, comprising:
 registering to a first network by a User Equipment (UE) in a Non-Terrestrial Networks (NTN) system with discontinuous coverage, wherein the UE is in an automatic network selection mode;   starting a timer T at time t1 for attempting to obtain service from a second network with a higher priority than the first network, wherein the timer T is configured to expire at time t3;   determining that the UE is out of coverage at time t2 that is before time t3, and in response the UE deactivates access stratum functions for power saving at time t2; and   triggering an attempt to obtain service from the second network at a subsequent time t4 that is later than time t3, and wherein the access stratum functions remain deactivated at time t3.   
     
     
         2 . The method of  claim 1 , wherein the first network is a VPLMN, and wherein the second network is a home PLMN (HPLMN) or an equivalent HPLMN (EHPLMN). 
     
     
         3 . The method of  claim 1 , wherein the UE determines that the UE is out of coverage based on ephemeris data broadcasted from satellites in the NTN system. 
     
     
         4 . The method of  claim 3 , wherein the ephemeris data is included in system information block (SIB) including SIB-3, SIB-31, or SIB-32. 
     
     
         5 . The method of  claim 1 , wherein the UE keeps the timer T running with an original time out value and the timer T expires at time t3. 
     
     
         6 . The method of  claim 5 , wherein the UE triggers the attempt to obtain service from the second network upon the UE activates the access stratum function. 
     
     
         7 . The method of  claim 5 , and wherein the UE triggers the attempt to obtain service from the second network after the UE activates the access stratum functions. 
     
     
         8 . The method of  claim 1 , wherein the UE prolongs the timer T to have a new time out value such that the timer T expires at the subsequent time t4, and wherein the UE triggers the attempt to obtain service from the second network upon the timer T expiry. 
     
     
         9 . The method of  claim 8 , wherein the UE activates the access stratum functions at time t4. 
     
     
         10 . The method of  claim 8 , wherein the UE activates the access stratum functions before time t4. 
     
     
         11 . A User Equipment (UE), comprising:
 a registration circuit that registers to a first network in a Non-Terrestrial Networks (NTN) system with discontinuous coverage, wherein the UE is in an automatic network selection mode;   a timer T that is started at time t1 for attempting to obtain service from a second network with a higher priority than the first network, wherein the timer T is set to expire at time t3;   a control circuit that determines that the UE is out of coverage at time t2 that is before time t3, and in response the UE deactivates access stratum functions for power saving at time t2; and   a network selection circuit that triggers an attempt to obtain service from the second network at a subsequent time t4 that is later than time t3, and wherein the access stratum functions remain deactivated at time t3.   
     
     
         12 . The UE of  claim 11 , wherein the first network is a VPLMN, and wherein the second network is a home PLMN (HPLMN) or an equivalent HPLMN (EHPLMN). 
     
     
         13 . The UE of  claim 11 , wherein the UE determines that the UE is out of coverage based on ephemeris data broadcasted from satellites in the NTN system. 
     
     
         14 . The UE of  claim 13 , wherein the ephemeris data is included in system information block (SIB) including SIB-3, SIB-31, or SIB-32. 
     
     
         15 . The UE of  claim 11 , wherein the UE keeps the timer T running with an original timeout value and the timer T expires at time t3. 
     
     
         16 . The UE of  claim 15 , wherein the UE triggers the attempt to obtain service from the second network upon the UE activates the access stratum function. 
     
     
         17 . The UE of  claim 15 , and wherein the UE triggers the attempt to obtain service from the second network after the UE activates the access stratum functions. 
     
     
         18 . The UE of  claim 11 , wherein the UE prolongs the timer T to have a new timeout value such that the timer T expires at the subsequent time t4, and wherein the UE triggers the attempt to obtain service from the second network upon the timer T expiry. 
     
     
         19 . The UE of  claim 18 , wherein the UE activates the access stratum functions at time t4. 
     
     
         20 . The UE of  claim 18 , wherein the UE activates the access stratum functions before time t4.